Washing methods are known where the washing solution is circulated continuously during the washing process and conducted through one or more vessels in which the entrained soil can settle from the solution before it is returned into the washing process. It has already been suggested to provide screens or filters in the conduits through which the solution is circulated to retain coarse impurities or objects which could damage the mechanism. But since the bulk of the soil is usually dissolved in the washing solution or is dispersed in very fine distribution therein, cleaning or regeneration of the washing solution in this way is inadequate, and savings in certain of the washing and cleaning ingredients, for example, phosphates, can only be achieved at the expense of cleaning results.
In commercial laundries it is customary to prepare the washing solution with softened make-up water, the water used being first treated with an ion exchanger. But soft water does not have sufficient washing power even when containing surface-active agents, particularly since the soil adhering to clothes, etc. contains as a rule considerable amounts of hardness formers which are not sufficiently detached in the absence of calcium binding substances, which results in progressive incrustation of the material being washed. Furthermore it has been suggested to carry out the washing process in the presence of ion exchangers of the organic polymer type. The ion exchangers are added to the washing solution either in the form of textile-structures (i.e., textiles having a content of calcium-binding components) or as granular or powdered exchange resins. However, textiles which contain ion exchange components have a low exchange capacity, so that large amounts are required. Moreover, the space occupied by the textile is at the expense of the objects to be washed. Granular to powdered ion exchange resins tend to be entrapped by the fabric or garment being washed, unless special precautions are taken, and the powders and granules are difficult to remove. If, as it has likewise been suggested, the exchange resins are enclosed in a gauze bag to prevent them from depositing on the textile fiber, the cleaning action of the solution is considerably decreased.